The main problem preventing me from merging this is that we don't have a way to check if the font we're trying to display a sample of is actually a.) loaded or b.) present on the user's system.

What we probably need to do is include a "blank" font as a data uri and use that as the fallback font. Then, we simply won't display a sample for fonts that the user doesn't have / aren't loaded.

An appropriate "blank" font that seems to work (from a technical perspective) is here: http://www.revitcity.com/forums.php?action=viewthread&thread_id=5267 . However, the rights around this font are unclear. I've asked the font team at Adobe whether they can make use a "blank" font really easily.